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9 changes: 9 additions & 0 deletions llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
#include <cassert>
#include <cstdint>
#include <iterator>
#include <map>
#include <memory>
#include <sstream>
#include <string>
Expand Down Expand Up @@ -213,6 +214,14 @@ class CounterExpressionBuilder {
/// Return a counter that represents the expression that subtracts RHS from
/// LHS.
Counter subtract(Counter LHS, Counter RHS, bool Simplify = true);

/// K to V map. K will be Counter in most cases. V may be Counter or
/// Expression.
using SubstMap = std::map<Counter, Counter>;

/// \return A counter equivalent to \C, with each term in its
/// expression replaced with term from \p Map.
Counter subst(Counter C, const SubstMap &Map);
};

using LineColPair = std::pair<unsigned, unsigned>;
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25 changes: 25 additions & 0 deletions llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,31 @@ Counter CounterExpressionBuilder::subtract(Counter LHS, Counter RHS,
return Simplify ? simplify(Cnt) : Cnt;
}

Counter CounterExpressionBuilder::subst(Counter C, const SubstMap &Map) {
// Replace C with the value found in Map even if C is Expression.
if (auto I = Map.find(C); I != Map.end())
return I->second;

if (!C.isExpression())
return C;

auto CE = Expressions[C.getExpressionID()];
auto NewLHS = subst(CE.LHS, Map);
auto NewRHS = subst(CE.RHS, Map);

// Reconstruct Expression with induced subexpressions.
switch (CE.Kind) {
case CounterExpression::Add:
C = add(NewLHS, NewRHS);
break;
case CounterExpression::Subtract:
C = subtract(NewLHS, NewRHS);
break;
}

return C;
}

void CounterMappingContext::dump(const Counter &C, raw_ostream &OS) const {
switch (C.getKind()) {
case Counter::Zero:
Expand Down
39 changes: 39 additions & 0 deletions llvm/unittests/ProfileData/CoverageMappingTest.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -291,6 +291,45 @@ struct CoverageMappingTest : ::testing::TestWithParam<std::tuple<bool, bool>> {
}
};

TEST(CoverageMappingTest, expression_subst) {
CounterExpressionBuilder Builder;
CounterExpressionBuilder::SubstMap MapToExpand;

auto C = [](unsigned ID) { return Counter::getCounter(ID); };
auto A = [&](Counter LHS, Counter RHS) { return Builder.add(LHS, RHS); };
// returns {E, N} in clangCodeGen
auto getBranchCounterPair = [&](Counter E, Counter P, Counter N) {
auto Skipped = Builder.subtract(P, E);
MapToExpand[N] = Builder.subst(Skipped, MapToExpand);
};

auto E18 = C(5);
auto P18 = C(2);
auto S18 = C(18);
// #18 => (#2 - #5)
getBranchCounterPair(E18, P18, S18);

auto E22 = S18;
auto P22 = C(0);
auto S22 = C(22);
// #22 => #0 - (#2 - #5)
getBranchCounterPair(E22, P22, S22);

auto E28 = A(A(C(9), C(11)), C(14));
auto P28 = S22;
auto S28 = C(28);
// #28 => (((((#0 + #5) - #2) - #9) - #11) - #14)
getBranchCounterPair(E28, P28, S28);

auto LHS = A(E28, A(S28, S18));
auto RHS = C(0);

// W/o subst, LHS cannot be reduced.
ASSERT_FALSE(Builder.subtract(LHS, RHS).isZero());
// W/ subst, C(18) and C(28) in LHS will be reduced.
ASSERT_TRUE(Builder.subst(Builder.subtract(LHS, RHS), MapToExpand).isZero());
}

TEST_P(CoverageMappingTest, basic_write_read) {
startFunction("func", 0x1234);
addCMR(Counter::getCounter(0), "foo", 1, 1, 1, 1);
Expand Down
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